Study On Seismic Impact Effect Of (32+24+32)m Railway Simply Supported Girder Bridges In High Intensity Areas

Because of the different span and different height of the main beam,the two adjacent beams of the simply supported girder bridges with different spans have different dynamic characteristics.In addition to the pounding of the two adjacent girders under strong earthquake,the pounding of girder piers may occur.In this thesis,based on the background of the simple supported girder bridge in bridge(2017)4301-Ⅳ(32+24+32)m,the longitudinal pounding model of simply supported girder bridge is established by Open Sees and Midas/Civil software the seismic response and mitigation measures of one sided and bilateral pounding of simply supported girder bridges with different spans in high intensity area are studied.The main work is as follows:(1)By referring to a large number of relevant literatures,the seismic impact response analysis method,adjacent structure pounding theory and bridge pounding buffer measures of railway simply supported beam bridge are summarized.(2)The influence of pounding effect on the longitudinal seismic response of unequal span simply supported girder bridge is studied in six cases: ignoring pounding,considering one sided beam-beam pounding,two sided beam pounding,beam-pier pounding,one sided beam-beam and beam-pier pounding,two sided beam-beam and beam-pier pounding.The results show that the pounding between adjacent beams of unequal span simply supported girder bridge will reduce the relative displacement between adjacent beams,and the pounding may affect the longitudinal displacement of single girder The impact of beam-pier pounding on the structure is similar to that of adjacent beam pounding,but the effect is weaker than that of adjacent beam collision;the impact of beam-pier pounding and adjacent beam pounding will reduce the impact response of each other.Compared with the bilateral impact,the peak impact force at the left expansion joint will increase significantly when considering the bilateral impact.(3)Taking the gap between adjacent beams,pier height,duration of earthquake motion,far-field and near-field effect of earthquake motion as variation parameters,the longitudinal seismic response of simply supported beam bridge with unequal span railway is studied.The results show that increase of gap between adjacent beams can effectively reduce the number of poundings between adjacent beams and the peak value of pounding force,but it will increase the relative displacement of two adjacent main beams,which is easy to cause beam falling;with the increase of pier height,the adjacent beam will be damaged The results show that the impact forces of beam and pier increase continuously;with the increase of important duration of ground motion,the seismic response of bridge structure becomes more obvious;the impact of near-field pulse seismic wave on structure is greater than that of near-field non pulse seismic wave,and greater than that of far-field seismic wave.(4)This dissertation analyzes the seismic response of restrainers,viscous damper and BRB device to railway simple supported girder bridge with unequal span.It is found that all the three limiting devices can reduce the seismic response of the bridge.The damping effect of viscous damper and BRB device with energy dissipation ability is obviously better than that of restrainers,and the control effect of BRB is better than that of viscous damper.